Pneumatic sound producing device



W. C. EAVES PNEUMATIG SOUND PRODUCING DEVICE sept. v30, 1947.

Filed sept. 2, 19.42

lNvENToR K i BWMM ATTORNEY Patented Sept. 30, 1941"? 4UNITED STATES ATENT orties William C. Eaves, Elyria, Ohio, assigner to Eaves Sound rrojectors, Inc., New York, N. Y., a corporation of Delaware Application September '2, 1942, Serial No. 457,057

9 Claims. 1

This invention relates to sound producing apparatus of the type wherein a stream of compressible fluid, such as air, is modulated to generate sound waves.

One of the objects f the invention is to provide a sound head of the fluid flow type embodying a novel balanced modulating valve.

Another object is to providel novel means for balancing the modulating valve of a sound head and for transmitting the balancing force to the movable member of the valve which means permit ready adjustment of the operative equilibrium position of the valve and add substantially no weight to the parts vibrating at the audio frequency of said valve.

A further object is to provide a novel air head which is so constructed that condensate or other moisture which tends to collect in the vicinity V`of the modulating valve will drain away, the

drain passage or passages being so disposed and arranged as not to interfere with the volume and quality of the sound reproduction.

A still further object is to provide novel means for mounting the movable member of a modulating valve of a sound head and for operatively connecting the actuating means of the sound head to said movable member.

Still another object is to provide a sound head unit wherein the operative elements are coinbined, arranged and interconnected in a novel manner to render the unit compact, economical to make and assemble, and capable of reproducing sound with kgreater delty for a given volume than has heretofore been possible in sound amplifying units of like character.

A still further object is to provide novel means for housing the above parts whereby assembly,

inspection, repair and adjustment are greatly facilitated.

Still another object is to provide a sound head of the air flow type with novel means for substantially eliminating resonant frequencies foreign to the frequency band being reproduced.

The above and :further objects and novel features of the invention will more fully appear vfrom the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended to dene the limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several Fig. 1 is a sectional view taken in a vertical plane along a center line of a sound head ernboolying the present invention;

Fig. 2 is a transverse horizontal ysectional view of the main housing of the sound head taken at the level indicated by section lines 2-.2 of Fig. 1; and

Fig. 3 is an exploded perspective view of the movable grid and the mounting therefor.

Referring to Fig. l, the novel sound head is illustrated as comprising a mainhousing l0 having a fluid chamber or passage I'I formed there# in, said chamber being shaped in the form of a reversed and inverted L, with the lower end of the vertical portion thereof having a fluid inlet I2 and the horizontal portion having a discharge passage I3. The walls of inlet I2 are preferably threaded to receive the end of a suit able conduit connected .to `a source of expansible iiuid at a pressure above atmospheric, as, Afor example, `an air pump (not shown). A horn mount I4 is rigidly secured to housing IU adjacent the end of discharge passage I3 and is adapted to constitute the throat portion of a suitable sound propagating device, such as an exponential horn (not shown), the latter being operatively secured to said mount, as by being threaded thereon at I5, Attached to the upper end of housing It and engaging horn mount I4 is a cup-shaped casing or cover plate It which forms a chamber 16a., the latter being adapted to receive the actuating mechanism of the .sound head. `A casing member I8 fixed to housing Iii below passage I3 provides a compartment ISa for suitable control means, said compartment communicating at the upper end thereof with the Y inlet portion of mount I4.

In order to impart sound producing characteristics to the air entering horn throat Ill, novel valve means for modulating an air stream flowing therethrough are disposed between the end of passage I3 and said horn throat. As shown, said means comprise a stationary grid member I9 mounted on housing Yl) across the open end of passage I3, said member having a plurality of vertical slots or ports ISa, (Fig. 2) formed therein and being secured to said housing, for example, by screws Zil. Pivotably mounted, in a novel manner to be more fully described hereafter, for cooperation with said stationary grid is a movable grid 2l (Figs. 1 and 3) constituted f by a rectangular body portion provided with a plurality of vertical slots 2id, each of said slots being located opposite the soiid areas between successive slots ISa. of the stationary grid. `To decrease the weight'of grid 2| and the depth of extending therethrough.

In order to mount grid 2| for pivotal movement about an axis perpendicular to slots 2|a, a novel resilient cantilever support is `.provided which, in the form illustrated, comprises a relatively thin, plate-like member 24 formed from a resilient ma terial, such as spring steel. Member 24 is rigidly secured to housing I below passage I3 (Fig. 1) by means, such as screws 25, in a plane substantially perpendicular to the face of grid I9 and has a portion thereof extending beyond the front face of said grid, said portion being provided with a central recess26. Two arms 24a (Fig. 3) are thus formed in the free end of member 24 and are secured by screws 2l (Fig. 1) to the lower edge of grid 2| on opposite sides of lug 22, the latter projecting downwardly through recess 26 and being adapted for engagement with a balancing mechanism in a manner more fully described hereafter. Member 24 thus constitutes a cantilever suspension which normally tends to maintain the face of grid 2| in engagement with the face of grid I9 and to resiliently oppose any force tending to pivot grid 2| in a counterclockwise direction, as viewed in Fig. 1.

In order to vibrate grid 2| and modulate the air stream flowing through valve |9, 2|, imparting sound producing characteristics thereto, an electromagnetic actuating mechanism 2l, for example, of the magnetic type comprising an armature 28, is mounted in chamber |6a, said armature being vibrated in accordance with electric current undulations initiated by suitable means, such as the microphone of an amplifying unit (not shown). Armature 28 has the lower end thereof connected to one end of a grid driving link 2g, the other end of said link being threaded Y into recess 23a of lug 23 so that vibrations of armature 23 are transmitted to grid 2| in a direction substantially perpendicular to the face of said grid producing a corresponding vibration of said grid about its pivotal axis.

It is preferable to have grid I9 formed so that it lprojects upwardly beyond the to-p surface of housing I!! and to have the upper edge portion of said grid engaging the inner face of mount Hl,

thereby providing a protective: wall S between the interior of said mount and chamber 16a. An aperture 30a is provided in said wall for link 29 and the space between said link and the wall of said aperture is preferably filled with a ring or grommet 39h of suitable non-resonant, resilient material such as rubber. As a result, air leakage into chamber |6a, from the interior of horn mount I4, is substantially eliminated, preventing the admission of moisture into said chamber and avoiding any loss in efficiency oi sound reproduction.

When air under pressure discharges from passage |3 through grid |9, a force is applied to grid 2|, tending to Ipivot the latter in a counterclockwise direction, as viewed in Fig. 1. To partially counterbalanoe the effect of this force and establish an open equilibrium position for grid 2|, pressure responsive balancing means are provided and connected in a novel manner to said grid. In the form illustrated, said means comprise a diaphragm 32 mounted in the vertical wall portion of casing li! beneath passage 3 so as to be subject to the difference between the pressure in air chamber and the atmospheric pressure in compartment |8a, said diaphragm being held in fluid-tight engagement with a shoulder 33 in said casing by an annular member 34, which is, in turn, secured to said casing by screws 35. A pressure transmitting contact block 3S of suitable, non-resonant material, such as rubber, is mounted on diaphragm 32 and is connected to grid 2| by means of an arm 3l pivotably mounted at its lower end on the shank of a screw 38, the latter being threaded into casing I9. A recess Sla having convex walls is preferably provided in said arm to receive said screw shank thereby permitting pivotal movement of said arm about an axis perpendicular to the axis of said screw. Arm 31 has a screw 39 threaded therethrough at a point substantially opposite the center of diaphragm 32, block 35 being adapted to engage the end of'said screw to actuate said arm in accordance with the air pressure in chamber Mounted at the upper end of arm 3l for transmitting pressure from the latter to grid 2| is a block 4U of non-resonant material, such as rubber, said block being of suiiicient size to substantially ll the upper end of chamber |8a with one side thereof engaging lug 22 and the upper end thereof engaging member 24. Accordingly, in addition to transmitting forces from arm 3T to grid 2|, block 48 acts to seal chamber |8a from the air stream passages and to dampen resonant free -quencies which might otherwise be set up in member 24 and in the pressure transmitting linkage between the diaphragm block 36 and grid 2|.

To prevent accumulation of moisture in horn mount i4 and between valve grids 9 and 2|, a suitable drainage passage 4| is provided. As shown, said passage communicates at its upper end with substantially the lowest point on the interior of said horn mount and pro-jects downward through said mount and cover I8, thereby eliminating the ypossibility of water accumulation at the horn mount and valve. The upper end of passage 4| is disposed opposite the lower end of lug 22 where substantially no air iiow or current exists and, accordingly, said passage has a negligible eiect on the amplitude and fidelity of the sound reproduction. i

In order to heat grid valve |9, 2| and the air approaching said valve, heating means j are mounted in a novel manner in the sound head, saidmeans, as shown, comprising a pair of heating coils 42 (Fig. 2) extending vertically through housing IB from the upper end thereof and located adjacent said valve on opposite sides of .cham-ber |8a. Thus, the air entering chamber is progressively heated as it approaches/the grid valve and, in addition, the valve parts aswell as the balancing mechanism and the connection between said mechanism and saidV partsl are heated. Accordingly, precipitation of moisture due to the throttling action of the valve is minimiz`ed and the possibility of improper functioning of the movable parts of the sound head due to icing is eliminated. v r

In operation, air under pressure is4 admitted to chamber through inlet |2 and acts to' pivot grid 2| in a. counterclockwise direction, as viewed in Fig. 1. This pivotal movement is opposed .by cantilever 24 and by the balancing mechanism comprising diaphragm 32. The latter tends to move to the left with the admission of high pressure air into chamber and by engaging .the end of screw 39 to apply a force to arm 31, which force pivots the latter in a counter-clockwise direction. This counter-clockwise torque is,in turn, transmitted through block di) to lug 22,:applying a clockwise torque to grid2l.` A'Ihe'torques exerted by member 24 and the balancing mechanism on grid ZI increase in magnitude as the angular displacement of said grid increases so that at a predetermined angular position of said grid these torques set the latter in equilibrium,

. Vibrations transmitted to grid 2l by armature 28 of actuating means 21 are thereafter .accu-Y rately reproduced in. said grid and are .effective to impart sound producing characteristics to the air stream.

It is to be noted that the force transmitted to arm 3l by diaphragm 32 for a given pressure in. chamber Il depends on the axial position of screw 39 relative to said arm. Accordingly, screw 39 constitutes a simple and convenient means for adjusting the magnitude of the balancing force applied to grid 2| and serves to establish operative equilibrium or neutral position of grid 2|. In the event the actuating mechanism for imparting vibrations to valve I9, 2l is of the dynamic type, screw 39 becomes the chief means for establishing a desired operative equilibrium position of valve member 2l.

The efficiency and iidelity of sound reproduction in the above described unit, are greatly increased by minimizing the mass subject to the audio-frequency vibrations imparted by the actuating means to the valve, This is accomplished by providing the relatively short connecting link 29 as the only motion transmitting member between grid 2l and armature 28 and by the arrangement of the valve balancing means whereby screw 39 and balancing arm or beam 3l are isolated from diaphragm 3d and grid 2| by nonresonant members 38 and lill which nevertheless act to transmit a balancing torque to said grid. The isolation of the balancing mechanism from the pressure responsive diaphragm practically obviates feed-back howls which are so diiiicult to control in conventional sound projecting devices. It is to be additionally noted that the balancing force, the force of the air stream, and the actuating force are applied to grid 2l substantially parallel to the plane of supporting plate 2@ and in the direction ci the free or supporting end of the latter. Accordingly, said plate is maintained under tension during operation and provides a pivot for grid 2l which insures substantially true arcuate movement of said grid during operation.

There is thus provided a novel sound head of the air flow type having a balanced modulating valve mounted and actuated in a novel manner so as to reproduce sound with great iidelity and volume. The weight of the parts adapted to vibrate with the movable valve member and the pressure responsive control diaphragm is maintained at a minimum so as to substantially eliminate feed-back howls and improve the iidelity of reproduction. The modulating valve and the actuating and balancing mechanisms therefor are arranged and combined in a novel manner to be readily and economically constructed and assembled, and to have the parts thereof available for ready inspection, repair and replacement. There is also provided novel means for pivotably mounting the movable member of a modulating valve whereby the latter moves in a true arc during operation, and means for insuring proper operation of said valve under adverse weather conditions.

Although only a single embodiment of the 1nvention is illustrated and described, it is to be expressly understood that the same is not limited thereto, For example, it will now be' apparent to those skilled in the art that instead of.- the armature of a magnetic actuating unit, thevoice coil of a dynamic unit may be connected to the modulating valvel to actuate .the latter. More over, a suitable resilient member of non-.reso-A nant material may be interposed between the lower end of arm .31 and housing i9 to maintain said arm against the head of screw 38.. Various otherchanges may be made in the .desi-gn and arrangement of parts without departing from the spirit and scope of the invention'. For av defini` tion of the limits of the invention, referencefwilll be had primarily to the appended claims.

What .is claimedl is:

1. In a'sound head of the type described, valve mechanism including` .a flat movable gridmem-V ber, and a cantilever secured to one end of said member for pivotally mounting the same, actu-v ating means for the grid member including .a .rod rigidly secured to said member, and means for balancing .said member, said actuating means and said balancing means being so constructed and arranged. as to apply 4forcesto said member on opposite sides of said cantilever in a direction substantially parallel to the plane of saidv canti lever.

2. In an air head, means comprising a passage for a fluid stream, a grid valve for modulating said stream, said valve comprising a movable grid, a suspension plate secured as a cantilever to said means and having the free end thereof xed to said grid to -s'erve as a resilient hinge therefor, actuating means connected to the edge of said grid opposite the edge mounted on said plate, and balancing means for opposing the pivotal effect on said grid of the fluid stream, said balancing means comprising a pressure responsive member connected with said passage and the atmosphere, a pivotable link fulcrumed at the end thereof remote from said grid, a non-resonant member adapted to operatively connect said link to said grid and a second non-resonant member adapted to transmit forces from said pressure responsive member to said link, said first-named resonant member engaging said plate to dampen resonant vibrations thereof.

3. In a sound head wherein a fluid stream is modulated by a grid valve, means for balancing the movable grid of said valve comprising a pressure-responsive diaphragm adapted to produce a balancing force in accordance with the pressure of said stream, a force transmitting mechanism, a non-resonant member operatively connecting said mechanism to said diaphragm, and a second non-resonant member operatively connecting said mechanism to said movable grid, said mechanism including an adjustable member adapted to control the balancing force applied to said movable grid to thereby control the balanced position of said grid.

4. In a sound head wherein a fluid stream is modulated by a grid valve, means for balancing the movable grid of said valve comprising a pressure-responsive mechanism adapted to produce a balancing force in accordance with the pressure of said stream, a lever, an adjustable element mounted in said lever, a member of nonresonant material secured to said mechanism, said element engaging said member to transmit the balancing force from said mechanism to said lever, and a member of non-resonant material mounted in said lever for applying the bala'ncv ing force to said movable grid,

5. In a sound head having a, grid Valve, means for balancing the movable grid of said valve comprising a force transmitting lever, a pressureresponsive diaphragm for applying the balancing force, a non-resonant member` connecting said diaphragm to said lever and a second nonresonant member connecting said lever to said movable grid to transmit the balancing force to the latter.

6. In a sound head wherein a fluid stream is modulated by a grid valve, means for balancing the movable grid of said valve comprising a diaphragm for producing a balancing force responsive to the pressure of said stream, a force transmitting member, a non-resonant member operatively connecting said `force transmitting member to said diaphragm, and a second nonresonant member for connecting'said force transmitting member to said movable grid.

7. In a sound rhead wherein a fluid stream is modulated by a grid valve including a movable grid, a plate-like cantilever support for pivotally mounting said grid with the slotted portion 'of said grid disposed on one side of said support in the fluid stream, said support being mounted to have its free end extending parallel to and in the direction of said uid stream, and means for balancing said grid in said stream, said means being connected to said grid on the opposite side of said support from said slotted portion and applying a balancing forceto' said grid parallel to and in the direction of said stream.

8. In a sound head of the grid valve type, ba1` ancing means for the movable member ofthe grid valve comprising a diaphragm subjected to the fluid pressure acting on said movable menti ber, a lever for transmitting pressure from the diaphragm to said movable member, and nonresonant means operatively connecting said lever to said diaphragm and movable member.

9. In a sound head of the grid valve type, balancing means for the movable member of the grid valve comprising a diaphragm subjected to the iuid pressure acting on said movable member, a lever for transmitting pressure from the diaphragm to said movable member, non-resonant means operatively connecting said lever to said diaphragm and to the movable member, and means operatively connected to` said lever for adjusting the neutral position of said movable member.

' WILLIAM C. EAVES.

REFERENCES CITED The following references are of record in the lle of this patent:

UNITED STATES PATENTS Number Name Date 1,898,302 Hetze] Feb. 21, 1933 2,141,208 Eaves Dec. 27, 1938 2,212,210 Mesinger Aug. 20, 1940 2,015,977 Thrall Oct. 1, 1935 2,140,293 Kolb et al. Dec. 13, 1938 2,371,960 Eaves Mar. 20, 1945 1,143,092 Unckles June 15, 1915 1,717,012 Dixon June 11, 1929 1,323,999 Baker Dec. 2, 1919 2,271,307 Ray Jan. 27, 1942 2,384,371 Dilks Sept. 4, 1945 1,148,619 Pierman Aug. 3, 1915 

